Many women, from the age of thirty-five, and more particularly after the menopause, frequently complain of dryness of their skin, and of unattractive or uncomfortable manifestations resulting therefrom (desquamation, dull complexion, cutaneous atony). Now, as is now known, this dryness is caused by a decrease in the production of sebum with age.
Sebum is the natural product of the sebaceous gland which, together with the sweat produced by the eccrine or aprocrine glands, constitutes a natural moisturizer for the epidermis. It consists essentially of a more or less complex mixture of lipids. Conventionally, the sebaceous gland produces squalene, triglycerides, aliphatic waxes, cholesterol waxes and possibly free cholesterol (Stewart, M. E., Semin. Dermatol. 11, 100–105 (1992)). The action of bacterial lipases converts a variable portion of the triglycerides into free fatty acids.
Sebocytes are the competent cells of the sebaceous gland. The production of sebum is associated with the programme of terminal differentiation of these cells. During this differentiation, the metabolic activity of the sebocytes is essentially focused on the biosynthesis of lipids (lipogenesis) and more specifically on the neosynthesis of fatty acids and squalene.
A compound for stimulating the production of the lipids that form sebum, by the cells of the sebaceous gland (the sebocytes), would therefore be of definite advantage for the treatment of oligoseborrheic dry skin, i.e. skin with a sebum content of less than 100 μg/cm2 on the forehead.
To this end, it has been proposed in patent U.S. Pat. No. 4,496,556 to use DHEA, a steroid secreted by the adrenal glands, or its esters, administered topically, to increase the production of sebum.
However, due to regulatory matters, it is not always possible to use compounds of this type in cosmetics. In addition, its efficacy is insufficient for oligoseborrheic skin. There is thus still a need for cosmetically acceptable compounds allowing the sebaceous function to be efficiently stimulated, for the purpose of treating oligoseborrheic dry skin.
Such compounds would also be useful in the treatment of a dry scalp, which is often associated with dull, lifeless hair.